Hi. I just came with the idea of my own expansion/story. This is just an idea (maybe someone from Blizzard will like it and someday use it for real). Feel free to comment. I apologize for my poor englisch.

So the plot of my expansion take place on a whole new planet. Let's say The Horde and The Alliance built some like Exodar-thing starships, powerfull portals or used magic to travel thru the Twisting Nether... and then things gone bad. Ships crashed/portals collapsed etc. As a hero you were sent with the expedition to conquer new lands but merely no one escaped death.

You start on the new planet - with no gear just like in Vanilla. You're on your own, you need to survive. You're enemy crushed on the other side of the globe. The planet is pretty much like Azeroth, but there is no signs of high civilisation. Only small, bigger tribes of new interesting races. As you do quests for the tribes and gearing up - you discover that there are some barbaric bad guys which live in a fortress of a local powerfull alien-warlock/necromancer and there are 3 ancient-titan-like artifact that can be used in creating a thing that will bring you home, back to the Azeroth.... of course it will not be so easy, because the fortress is heavilly guarded and the alien-warlock just joined Burning Legion and sold this planet to the demons (for greater power).

The bad guys have all 3 of the artifacts and manage to build a couple of portals, but heroes somehow steal one artifact from the fortress (in a quest/dungeon/scenario) in a suicide mission and made another portal to Azeroth. The story ends with an EPIC battle between Azeroth + tribes forces against the Burning Legion + alien-warlock/necromancer forces.

The battle will take place in a open world. The Fortress will be the end-game raid.

That's pretty much the story. Now features:

-New planet: I imagine it being huge with very tall black buildings(for the bad guys), trees, wooden towers, stone towers. Lot's of lower temperate coniferous forests, lakes, marhslands. Some dark areas like Duskwood, and stony like Deadwind Pass like areas. Ritual shrines in the forest. Mostly Pagan/barbaric theme with a little bit of cosmic twist

- Air battles (part of world pve/pvp/quests/dungeons/raids)

- No new races (but player can play them as as a part of quest like it was with Naga etc.) I was thinking about some alien-weasel-humanoid race/ skeleton minions/ blue fur beast-like race. (I'm not good at drawing things )

- No new classes

- More enviromental/survival quests. For example there's a bridge, but it's broken and you must find someone (an alien-lumberjack) in the village tha can help you repair the bridge, but he wont help you until you do something for him. I think about some good mix between those type of quests and the random (go to the village- take all quests and be back when you're done). OR There are some types of the shrines tha can send player into death realm and then he/she can do some quests only in the spirit world. Quests with the dark humour are always fun